Spontaneous formation of linearly arranged microcraters on sol-gel-derived silica-poly(vinylpyrrolidone) hybrid films induced by Bénard-Marangoni convection

Complex, sophisticated surface patterns on micrometer and nanometer scales are obtained when solvent evaporates from solutions containing nonvolatile solutes dropped on a solid substrate. Such evaporation-driven pattern formation has been utilized as a fabrication process of highly ordered patterns in thin films. Here, we suggested the spontaneous pattern formation induced by Bénard-Marangoni convection triggered by solvent evaporation as a novel patterning process of sol-gel-derived organic-inorganic hybrid films. Microcraters of 1.0-1.5 μm in height and of 100-200 μm in width were spontaneously formed on the surface of silica-poly(vinylpyrrolidone) hybrid films prepared via temperature-controlled dip-coating process, where the surface patterns were linearly arranged parallel to the substrate withdrawal direction. Such highly ordered micropatterns were achieved by Bénard-Marangoni convection activated at high temperatures and the unidirectional flow of the coating solution on the substrate during dip-coating.     

Enhanced near-field distribution inside substrates mediated with gold particle: optical vortex and bifurcation

We present new results for laser excited semiconductor crystals probed by ultrashort x-ray pulses diffracted by the crystal lattice. First we discuss acoustical phonons of semiconductors, i.e. indium antimonite and germanium, and then we describe the temporal evolution of the laser-induced metal–semiconductor phase transition of samarium sulfide.     

Fragment Molecular Orbital method-based Molecular Dynamics (FMO-MD) as a simulator for chemical reactions in explicit solvation

Fragment Molecular Orbital based-Molecular Dynamics (FMO-MD, Komeiji et al., Chem Phys Lett 2003, 372, 342) is an ab initio MD method suitable for large molecular systems. Here, FMO-MD was implemented to conduct full quantum simulations of chemical reactions in explicit solvation. Several FMO-MD simulations were performed for a sphere of water to find a suitable simulation protocol. It was found that annealing of the initial configuration by a classical MD brought the subsequent FMO-MD trajectory to faster stabilization, and also that use of bond constraint in the FMO-MD heating stage effectively reduced the computation time. Then, the blue moon ensemble method (Sprik and Ciccotti, J Chem Phys 1998, 109, 7737) was implemented and was tested by calculating free energy profiles of the Menschutkin reaction (H3N + CH3Cl --> +H3NCH3 + Cl-) in the presence and absence of the solvent water via FMO-MD. The obtained free energy profiles were consistent with the Hammond postulate in that stabilization of the product by the solvent, namely hydration of Cl-, shifted the transition state to the reactant-side. Based on these FMO-MD results, plans for further improvement of the method are discussed.     

Photophysics and Inverted Solvatochromism of 7,7,8,8-Tetracyanoquinodimethane (TCNQ)

We report absorption, fluorescence, and Raman spectroscopy of 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a variety of solvents. The fluorescence quantum yields (QYs) of linear alkane solutions are similar to one another, but QY is shown to acutely decrease in other solvents with increasing polarities. The slope of the solvatochromic plot of absorption maxima is inverted from negative to positive with an increase in solvent polarity. A significant change in the frequency of carbon-carbon double bond stretching modes is not observed in Raman spectra of TCNQ in different solvents. The molar absorption coefficient is determined to calculate the oscillator strength of the absorption band. The radiative decay rate constant calculated from the oscillator strength is approximately ten times larger than that elucidated from the fluorescence lifetime and QY. These spectroscopic parameters reveal that the relaxation occurs from a Franck-Condon excited state to a distinct fluorescence emissive state with a smaller transition dipole moment.     

Asymmetric syntheses and applications of planar chiral hypervalent iodine(V) reagents with crown ether backbones

Novel optically active hypervalent iodine(V) reagents with planar chiral crown ether backbones were synthesized using the intramolecular Huisgen reaction as a key step and l-methyl lactate as the source of chirality. The relative configurations of these reagents and stabilities of planar chiralities were determined by DFT calculations. These planar chiral reagents were applied to the hydroxylative dearomatization/[4 + 2]-dimerization reactions of phenols to afford bisthymol and biscarvacrol, a natural product, with moderate enantioselectivities.     

Ab initio fragment molecular orbital (FMO) method applied to analysis of the ligand-protein interaction in a pheromone-binding protein

Full quantum computation of the electronic state of proteins has recently become possible by the advent of the ab initio fragment molecular orbital (FMO) method. We applied this method to the analysis of the interaction between the Bombyx mori pheromone-binding protein and its ligand, bombykol. The protein–ligand interaction of this molecular complex was minutely analyzed by the FMO method, and the analysis revealed several important interactions between the ligand and amino acid residues.     

Synthesis,Characterization, and Catalytic Activity of a Cubic [Mo3S4Pd] Cluster Bearing Bulky Cyclopentadienyl Ligands

A cubic metal-sulfur cluster containing three Mo ions and a Pd ion, [Cp^SiEt3₃Mo₃S₄Pd]Cl ( Mo₃Pd , Cp^SiEt3=C₅Me₄SiEt₃), was synthesized by the incorporation of the Pd ion into a Mo₃S₄ cluster [Cp^SiEt3₃Mo₃S₄] ( Mo₃ ). Mo₃Pd was characterized by ¹H NMR, UV-vis, X-ray crystallography, and cyclic voltammetry measurements. The electrochemical measurements demonstrated reversible one- and two-electron reduction processes for Mo₃Pd , which suggested potential catalytic activity for two-electron substrate reductions such as hydrogen evolution reaction. Controlled potential electrolysis in the presence of Mo₃Pd and trifluoroethanol in THF solvent displayed H₂ formation with a constant current over 60 min. The amount of generated H₂ by Mo₃Pd was two times higher than Mo₃ , indicating the catalytic activity facilitated by the Pd center. The mechanism of the catalytic cycle was determined by density functional theory.     

Radical/Iminium Domino Strategy (RIDS) for Rapid Construction of Sterically Congested γ-Lactam-Based Multiheterocycles

Cu-Catalyzed radical/iminium domino strategy (RIDS) for the efficient synthesis of quaternary-carbon-containing γ-lactam-based multiheterocyclic structures from α-bromocarboxamides is reported. This domino reaction strategy enables the construction of multiheterocycles in one step. Mechanistic studies showed that two catalytically generated iminiums are likely to be key intermediates in the catalytic cycle. The developed method can be used in a chemoselective manner to produce multicyclic products in the reaction with ketones possessing two different carbonyls.